Install and configure DenyHost
Brute force attacks or dictionary based attacks are common these days for servers. DenyHosts is an excellent python tool to prevent such attacks. It will detects failed attempts and prevent offending Host/IP for further connection by adding it to /etc/hosts.deny file.
Here are steps to install and configure DenyHosts for your server. These steps are applicable for Red Hat based distros (ie RHEL, CentOS, Fedora) and needs minor changes for other distros. You can copy paste the commands.
Step 1. Detect which version of Python is installed on your server:
# python -V